Implement en/fr localization across admin and user UIs

Introduce client-side localization helper and en/fr locale bundles.

Route admin control, picks, movies, stats, winners and settings UIs through i18n keys instead of hardcoded text.

Remove French text from the English UI and standardize shared messages (saving, network errors, confirmations).

Update .gitignore to ignore editor metadata and localization helper artifacts.

public/js/app_register.js

@@ -2,6 +2,22 @@ function decodeJwt(token) {
   return JSON.parse(atob(token.split('.')[1]));
 }
 
+function translateApiMessage(messageKey, message, fallbackKey, fallbackText) {
+  try {
+    if (window.i18n && typeof window.i18n.t === 'function') {
+      if (messageKey) return window.i18n.t(messageKey);
+      const map = {
+        'Mauvais nom de chien': 'auth.dogAnswerIncorrect',
+        "L'utilisateur s'est enregistré avec succès !": 'auth.registrationSuccess',
+        'User registered successfully!': 'auth.registrationSuccess',
+      };
+      if (message && map[message]) return window.i18n.t(map[message]);
+      if (fallbackKey) return window.i18n.t(fallbackKey);
+    }
+  } catch (_) {}
+  return message || fallbackText || '';
+}
+
 async function applyActiveOscarYearToTitle() {
   const base = 'Pool Oscars';
   const current = String(document.title || base);
@@ -92,7 +108,12 @@ initPage();
     if (res.ok) {
       const data = await res.json();
       // Show success message in the modal
-      responseMessageElement.textContent = data.message;
+      responseMessageElement.textContent = translateApiMessage(
+        data?.messageKey,
+        data?.message,
+        'auth.registrationSuccess',
+        'User registered successfully!'
+      );
       
       // Show the modal
       modal.show();
@@ -104,7 +125,11 @@ initPage();
     } else {
       const error = await res.json();
       // Show error message in the modal
-      responseMessageElement.textContent = `Error: ${error.message}`;
+      const prefix = (window.i18n && typeof window.i18n.t === 'function')
+        ? window.i18n.t('common.errorPrefix')
+        : 'Error:';
+      const msg = translateApiMessage(error?.messageKey, error?.message, 'common.errorOccurred', 'An error occurred');
+      responseMessageElement.textContent = `${prefix} ${msg}`.trim();
       
       // Show the modal
       modal.show();